Multiple-view displays are known for providing autostereoscopic three dimensional image display and for displaying different images in different directions for different viewers. Examples of multiple-view displays are disclosed in EP 0 829 744, GB 2 390 172 and EP 1 427 223.
WO 2006/043720 discloses a multiple-view display for use in a vehicle. A technique is disclosed for improving image quality so as to improve, for example, brightness, contrast and scale of each image.
U.S. Pat. No. 6,973,210 and US 2005/0238228 disclose a technique for mapping composite colour pixel groups to colour component pixels using lowpass filters to achieve a desired degree of luminance and colour accuracy. This technique requires a continuous three channel input signal or a discrete input which has a higher sampling frequency than is required by the output (or which has been scaled to have a higher sampling frequency than the output). Sampling of the filtered result is handled by selecting spatially different regions of the image data and mapping them to the colour component pixels rather than to the composite pixel groups.
US 2003/0210829 discloses a technique for enhancing image quality using a combination of horizontally and vertically applied highpass and lowpass filters.
US 2006/0158466 discloses an image processing technique for displaying images on a display having fewer pixels than in the original image. This technique seeks to reduce the number of driving integrated circuits required on the display.
Jinsung OH, Changhoon LEE and Younam KIM, “Minimum-Maximum Exclusive Weighted-Mean Filter with Adaptive Window”, IEICE TRANS. FUNDAMENTALS, Vol. E88-A, No. 9, September 2005, pages 2451-2454 disclose an adaptive filter for removing impulse noise from corrupted images. A conditional filter is applied depending on whether noise is detected. If noise is not detected, the unprocessed pixel value is used. If noise is detected, the pixel value is replaced by a weighted sum of adjacent pixel values not affected by noise.
WO06110646A2 discloses an autostereoscopic display using a slanted lenticular component and a method of improving image quality by applying “bleed-through” and blurring. “Bleed-through” occurs when data for a pixel for a given view is also visible in a neighbouring view. This may be because the arrangement of the lenticular component is such that a pixel is physically visible in both views or, by processing the image, data from one view is overlaid on a neighbouring view, for example by a blurring operation. Furthermore the blur function used in WO06110646A2 is a standard function such as that found in Photoshop image processing software.
Many known multiple-view displays are based on a display device in the form of a spatial light modulator, such as a liquid crystal device, whose pixel structure cooperates with a parallax optic, such as a parallel barrier or a lenticular screen, to control the viewing regions from which the pixels are visible. A typical example of such an arrangement is shown in FIG. 1 of the accompanying drawings. The individual colour component pixels (sub-pixel components) receive interlaced image data from two images to provide a two-view display. The red, green and blue pixels are indicated by R, G and B, respectively. The pixels displaying the first and second images are identified by the subscripts 1 and 2. The pixel structure is aligned with slits in a parallax barrier 1 so that only those pixels R1, G1 and B1 displaying the first image are visible to viewer 1 whereas only those pixels R2, G2 and B2 displaying the second image are visible to viewer 2.
Some undesirable colour artefacts may become visible for certain image features and an example of this is illustrated in FIG. 1. In this example, both views contain an image feature which is one composite colour pixel group wide as illustrated at 2. The adjacent composite colour pixel groups are black as shown, for example, at 3 and 4. The displayed feature is intended to be white. However, viewer 1 sees only the green component pixel G1 of this feature whereas the viewer 2 sees only the red and blue components of this feature. Thus, a feature which should appear to be white is perceived as being either green or magenta. Thus, for features such as narrow lines or “sharp” edges, incorrect colours may be perceived.
FIG. 2 of the accompanying drawings illustrates by way of example two types of parallax barrier displays. The type shown in the upper part of FIG. 2 at (a) is of the strip barrier type in which elongate slits extending throughout the height of the barrier are separated by opaque regions. The display shown at (b) in FIG. 2 has a different type of parallax barrier, in which the “slits” or apertures are arranged in a checkerboard pattern. The undesirable colour artefacts described hereinbefore can occur with either type of barrier, and with other barrier types and other types of parallax optics.